Stratigraphic sequence and characteristics of depositional system of the Beipiao Formation in the Beipiao (Jin-Yang) basin, western Liaoning

Sequence-stratigraphic and sedimentologic theories and methods were employed in the study of sequence stratigraphic features and sedimentary system distribution in the Beipiao Formation of the Beipiao (Jin-yang) basin. Based on comprehensive utilization of field outcrop and profile data, the authors established sequence stratigraphic framework and determined the types and distribution of sedimenatry facies. The result shows that the formation can be described as two three-order sequences, which can be divided into 7 quasi-sequence sets. Sedimentary facies comprising alluvial fans, braided river deltas and lake deposits were identified in the sequence. Depositional facies vary vertically from alluvial fans to braided river delta and then to lake facies and finally to delta. Horizontally, the facies present themselves as a nearly NW-SE-trending sedimenatry system, i.e., a sedimentary sequence comprising water transgression and regression. Paleogeomorphology controlled the sedimentary characteristics of the sediments of alluvial fans and climate affected the types of sediments and controlled the evolution pattern of the sediments in the formation.